I made some comparison gifs after the other thread, and I'd be willing to bet this is a hint of the new player character model.
Semi-large gifs so I'm linking them.
First off is cry. Notice the face comparison. Old one is stagnant and barely animated. New one is MoP level
No emote. Notice the face AND the hand animation
Talk-Exclamation variant. Either heavily modified or downright brand new.
Talk-question variant. Obviously a newer animation.
Run is amazingly better. Slowed down version
Sprint animation puts the old one to shame. Slowed down version
Something that the old model doesn't have.
It's very telling about Blizzards progress on the player models. I think it's supremely obvious that this Garrosh model is based off the new Orc Player models, not so much because of what he would need as a raid boss like run and sprint obviously, but stuff that he really wouldn't need to animate like the cry and roll animations.
Unless the Raid is extremely cinematic with a lot of Garrosh talking and crying, this could either be a product of the Machinima/Cinematics team making a new model to go into their pretty ingame cutscene. (Unlikely, as they didn't make a new one for the Horde MoP intro cinematic, arguably a better time to do it.) Or we just got ourselves a taste of what to expect from the new PC models.